The invention relates generally to computer operating systems, and deals more particularly with monitoring and handling of excessive demands on a CPU or services or resources within a computer system.
A computer system comprises many components, services and resources that support users/application programs. For example, every computer system includes one or more central processing units (CPUs) to execute application programs. Also, most computer systems include some type of operating system service to dispatch (i e. schedule) program tasks or threads for executions Also, most computer systems include I/O devices or resources such as DASD or printers for use by the application programs. Naturally. the speed that each components service and resource can serve a request is limited, and while the components service or resource is serving one requests other requests for the same components, service or resource may have to wait. The amount of waiting that can be tolerated and the penalty for waiting depend on the nature of the components, service or resource for which service is requested, the type of requester, and demands on other components, resources and services within the computer systems However, at some level or levels of waiting or utilization of the components, services and resources, system performance becomes unacceptable and safeguards must be installed to avoid such overuse of the computer system.
It was previously known to continuously monitor the demands on or utilizations of different components, services or resources such as CPU utilization., dispatcher queue length, number of active users, number of users in I/O wait queue and paging rate. When the demand or utilization exceeds a respective threshold for any individual component, service or resource the computer system signals the condition.
A drawback of this system is that each response is limited to demands on the respective individual component, service or resource irrespective of demands on the other components, services or resources, and this may not accurately represent overall system utilization/demand.
Accordingly, a general object of the present invention is to provide an exceptional condition handling system which more accurately and completely represents the composite level and nature of different types of demands on the computer system.
Another general object of the present invention is to provide an exceptional condition handling system which provides different types of responses depending on the level and nature of the demands on the computer system.